Apparatuses have long since been known for example for calcining solids (cf. EP 0 861 208 B1). In a fluidized-bed reactor the solids are treated with hot gases and calcined. The gas/solids mixture is discharged from the reactor via a transfer duct and separated in a centrifugal separator, in particular a cyclone, wherein the gases are withdrawn upwards and the solids are withdrawn downwards from the centrifugal separator. It was found out, however, that the formation of streaks at the inlet of the centrifugal separator has a negative influence on its segregation behavior.
In existing plants, the conduits merely were designed according to the requirements of the flow velocity at the inlet of the cyclone, whereas the formation of streaks was not taken into account.
U.S. Pat. No. 6,322,601 for example describes an inlet conduit for a cyclone, which is defined by an extrados face and an intrados face, wherein the intrados face is curved such that tangents mentally applied thereto intersect the extrados face at certain points. With the curved shape of the intrados face solid particles should be directed onto the extrados face and into the cyclone, in order to improve the acceleration efficiency. For further optimization, the intrados face can include grooves for guiding the solids flow. The flow velocity should be optimized thereby. A formation of streaks in the upper part of the cyclone is, however, not avoided.